U.S. Pat. No. 4,577,417, assigned to the same assignee as the present application, discloses a sole-and-heel structure having a premolded bulge under-the heel region, a premolded bulge under the metatarsal region and a passageway between the two bulges. Air in the cavities defined by the two bulges moves back and forth in the passageway.
The present invention involves premolded bulges in the heel portion only which bulges are connected by one or more passageways, or premolded bulges in the metatarsal portion only connected by one or more passageways, or passageway connected premolded bulges in both the heel portion and in the metatarsal portion, but without passageways between the bulges in the two portions.